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Bowhead Whale Balaena mysticetus

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Bowhead whales are supremely adapted to a life cycle spent entirely in the freezing, or near-freezing waters of the Arctic and sub-Arctic.  Found in both northern Atlantic and Pacific waters, the species has evolved thick skin and blubber for insulation and a source of energy reserves, an enormous, strong and bowed head that can break through ice up to 1 m thick, and an ability to stay under water for over an hour at a time to swim beneath the ice 1,2.  Although the bowhead is not the largest whale species, it is one the heaviest, and certainly the longest-lived. Evidence suggests that individuals can live up to 150, and perhaps even as long as 200 years2-4!

Once referred to as the ‘Greenland whale’, or the ‘Arctic right whale’, few commercial whale watching operations target this species because of its mostly remote habitat.  However, because it is a predominantly coastal, shallow-water species, it can be viewed from shore in some parts of its range.  Although not available to commercial whale watching, one of the longest standing population research projects on this species counts passing whales from an observation perch on a pressure ridge from the edge of shorefast ice in northern Alaska 5,6.  The bowhead whale is also one of the few whale species still subject to an ongoing aboriginal subsistence hunt, managed by the International Whaling Commission. 

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Not to be confused with:

In the Atlantic, bowhead whales could, at first glance, be confused with right whales, which also have smooth black backs without dorsal fins. However, the two species heads are very different, as bowhead whales lack the distinctive white callosities found on the top of right whales’ heads. Instead bowhead whale ‘chins’ are white, while right whales have dark chins and undersides.  In the Pacific, bowhead and gray whales overlap in the Bering, Chukchi and Beaufort seas, but gray whales are generally much slimmer and lighter in colour, and have pronounced ‘knuckles’ on their dorsal ridge.

Distribution  

There are currently four recognized stocks or breeding populations of bowhead whales: 1) A small genetically distinct population restricted to the Okhotsk Sea; 2) the Bering-Chukchi-Beaufort Seas stock (BCB) 3) the eastern Canadian-western Greenland Stock; and 4) the Spitsbergen Stock2.  Throughout the species’ range, bowhead whales are generally found in waters shallower than 200m, and often close to land, or sea ice 2,7.

Bowhead whales do not migrate as far as many other baleen whales. They migrate between wintering areas where mating/calving occurs to summer feeding areas, a distance of ~1500km for BCB bowheads.  The spring seasonal movements are typically northwards through the sea ice and along the ice edge to higher latitudes in the summer, and returning to more southerly areas of their range during the winter8,9.

Native to the following countries: Canada; Denmark (Greenland); Iceland; Norway; Russian Federation; United States (Alsaska)

Vagrant: France;  Ireland;  United Kingdom;.

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Biology and Ecology

Feeding

Bowhead whales feed predominantly on copepods, krill and other zooplankton, although there is some evidence that they can also feed on fish species, and bottom-dwelling crustaceans2,7,10.11. Bowhead whales often skim feed at the surface of the water, using their very long baleen plates (up to 5-6m) to filter out prey, even from less dense aggregations of zooplankton.  However, they can also feed in the middle of the water column, or even along the seabed7.10.

Social structure, reproduction and growth

Bowhead whales are normally found in groups of three or fewer animals, but can congregate in larger numbers where food is abundant and/or while migrating1. Mating is assumed to occur in March, and calves are born the following April or May after a 13-14 month long gestation period 2,5.  Females do not begin to have calves until they are roughly 25 years old12, and only give birth to one calf every 3-7 years13.   Calves are around 1000 kg at birth and must grow and acquire insulating blubber as quickly as possible.  Adult whales have a blubber layer up to 50cm thick, and calves grow more quickly in their first year than any other time in their lives8,9. Calves are weaned between 6 and 12 months2,9

Bowhead whales, like many baleen whales, also use sound to communicate under water 2,14. This renders the species vulnerable to disruption of feeding and communication when loud noises are generated from seismic surveys or other shipping and/or industrial activity in their habitat15.

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Research, threats and conservation status

Bowhead whales sometimes bear the scars typical of killer whale attacks, which are the only known natural predator of this robust whale species2.  Human-induced threats to bowhead whales include entanglement in fishing gear16-18, and increasingly, ship strikes and disturbance form underwater noise related to expansion of shipping, fishing, and oil and gas exploration in the Arctic as ice cover retreats19-21.  While bowhead whales may temporarily be benefiting from expanding feeding habitat associated with global warming and melting ice, it is unknown how this drastic change in habitat will affect populations in the long term22,23.  One consequence may be the merging and blending of Atlantic and Pacific populations that have been separated for generations, as recent years has seen the two come into contact with each other with the opening of the Northwest Passage24.

Conservation status

Bowhead whales were hunted for centuries, first by aboriginal groups in the Arctic, and then commercially for both their oil and their baleen9,25.  Commercial whaling for bowhead whales decimated stocks but has been prohibited under international conventions since the 1930s. Since that time the BCB subpopulation has been steadily increasing at a rate of roughly 3% per year6.   That population is now thought to number roughly 16,000 animals (See this IWC site for updated population estimates).  The species is globally considered of ‘Least Concern’ on the IUCN Red List of Threatened Species25.  However, the other three stocks are less numerous; the East Greenland-Svalbard-Barents Sea subpopulation is considered Endangered26 and Okhotsk Sea subpopulation is classified as Endangered27.  The species is listed on Appendix 1 of both the Convention on International Trade in Endangered species (CITES) and the Convention on Migratory Species (CMS).

Bowhead whales are subject to aboriginal subsistence hunts the US, Russia, Greenland and also Canada. The hunts in the US, Russia and Greenland are regulated by the International Whaling Commission (See this IWC table for annual catch numbers). The hunts in Canada are regulated by their Federal government in collaboration with Indigenous groups (Canada withdrew from the IWC in the 1981).

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Bowhead whales and whale watching

Bowhead whales can be viewed during day-trips from a few locations in Canada (e.g. Baffin Island). However, as a ‘shy species’ they are not often billed as the target of whale watching operations.  The species also occurs in   Greenland (Denmark) (esp. Disko Bay), and  Norway (Svalbard), as well as northern and northwestern Alaska (the United States).  However, because the species is often associated with the ice-edge, it is perhaps more likely to be viewed during live-aboard Arctic wildlife tours than day trips from these locations.

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References

Show / Hide References
  1. Jefferson, T. A., Webber, M. A. & Pitman, R. L. Marine Mammals of the World: a Comprehensive Guide to their Identification. Second Edition.  (San Diego: Academic Press, 2015).
  2. George, J. C., Rough, D. & Suydam, R. in Encyclopedia of Marine Mammals Vol. Third Edition  (eds B Würsig, J.G.M. Thewissen, & K.M. Kovacs)  133-135 (Academic Press, Elsevier, 2018 ).
  3. George, J. C. & Bockstoce, J. R. Two historical weapon fragments as an aid to estimating the longevity and movements of bowhead whales. Polar Biology 31, 751-754, doi:10.1007/s00300-008-0407-2 (2008).
  4. Rosa, C. et al. Age estimates based on aspartic acid racemization for bowhead whales (Balaena mysticetus) harvested in 1998–2000 and the relationship between racemization rate and body temperature. Marine Mammal Science 29, 424-445, doi:10.1111/j.1748-7692.2012.00593.x (2013).
  5. Barrow, Alaska. Marine Mammal Science 20, 755-773 (2004).
  6. Givens, G. et al. Estimate of 2011 abundance of the Bering-Chukchi-Beaufort Seas bowhead whale population. document presented to the Scientific Committee of the International Whaling Commission SC/65a/BRG01, 30 (2013).
  7. Fortune, S. M. E. et al. Seasonal diving and foraging behaviour of Eastern Canada-West Greenland bowhead whales. Marine Ecology Progress Series 643, 197-217 (2020).
  8. Schell, D. M., Saupe, S. M. & Haubenstock, N. Bowhead whale (Balaena mysticetus) growth and feeding as estimated by δ13C techniques. Marine Biology 103, 433-443, doi:10.1007/BF00399575 (1989).
  9. Finley, K. P. Natural History and Conservation of the Greenland Whale, or Bowhead, in the Northwest Atlantic. Arctic 54, 55-76 (2001).
  10. Lowry, L., Sheffield, G. & George, J. Bowhead whale feeding in the Alaskan Beaufort Sea based on stomach contents analyses. Journal of Cetacean Research and Management 6, 215-233 (2004).
  11. Heide-Jørgensen, M., Garde, E., Nielsen, N., Andersen, O. & Hansen, S. A note on biological data from the hunt of bowhead whales in West Greenland 2009–2011. Journal of Cetacean Research and Management 12, 329-333 (2012).
  12. George, J. C. et al. Age and growth estimates of bowhead whales (Balaena mysticetus) via aspartic acid racemization. Canadian Journal of Zoology 77, 571-580, doi:10.1139/z99-015 (1999).
  13. Rugh, D. J., Miller, G. W., Withrow, D. E. & Koski, W. R. Calving Intervals of Bowhead Whales Established Through Photographic Identifications. Journal of Mammalogy 73, 487-490, doi:10.2307/1382014 (1992).
  14. Clark, C. W. et al. Passive Acoustic Locations and Offshore Distribution of Bowhead Whales (Balaena mysticetus) during the spring of 2001 Census off Pt. Barrow, Alaska. 1-8 (2002).
  15. Blackwell, S. B. et al. Effects of Airgun Sounds on Bowhead Whale Calling Rates: Evidence for Two Behavioral Thresholds. PLoS ONE 10, e0125720, doi:10.1371/journal.pone.0125720 (2015).
  16. Clapham, P. J., Young, S. B. & Brownell Jr, R. L. Baleen whales: conservation issues and the status of the most endangered populations Mammal Review 29 35-60 (1999).
  17. Rolland, R. M., Graham, K. M., Stimmelmayr, R., Suydam, R. S. & George, J. C. Chronic stress from fishing gear entanglement is recorded in baleen from a bowhead whale (Balaena mysticetus). Marine Mammal Science 0, doi:10.1111/mms.12596 (2019).
  18. Thomas, P. O., Reeves, R. R. & Brownell, R. L. Status of the world's baleen whales. Marine Mammal Science, doi:10.1111/mms.12281 (2015).
  19. Moore, S. E., Haug, T., Víkingsson, G. A. & Stenson, G. B. Baleen whale ecology in arctic and subarctic seas in an era of rapid habitat alteration. Progress in Oceanography 176, 102118, doi:https://doi.org/10.1016/j.poce... (2019).
  20. Reeves, R. R. et al. Distribution of endemic cetaceans in relation to hydrocarbon development and commercial shipping in a warming Arctic. Marine Policy 44, 375-389 (2014).
  21. Reeves, R., Rosa, C., George, J. C., Sheffield, G. & Moore, M. Implications of Arctic industrial growth and strategies to mitigate future vessel and fishing gear impacts on bowhead whales. Marine Policy 36, 454-462, doi:http://dx.doi.org/10.1016/j.ma... (2012).
  22. Moore, S. E. & Huntington, H. P. Arctic marine mammals and climate change: impacts and resilience. Ecological Applications 18, S157-S165 (2008).
  23. George, J. C., Druckenmiller, M. L., Laidre, K. L., Suydam, R. & Person, B. Bowhead whale body condition and links to summer sea ice and upwelling in the Beaufort Sea. Progress in Oceanography 136, 250-262, doi:https://doi.org/10.1016/j.poce... (2015).
  24. Heide-Jørgensen, M. P., Laidre, K. L., Quakenbush, L. T. & Citta, J. J. The Northwest Passage opens for bowhead whales. Biology Letters 8, 270-273, doi:10.1098/rsbl.2011.0731 (2012).
  25. Cooke, J. & Reeves, R. Balaena mysticetus IUCN Red List of Threatened Species https://dx.doi.org/10.2305/IUC... (2018).
  26. 2Cooke, J. & Reeves, R. Balaena mysticetus (East Greenland-Svalbard-Barents Sea subpopulation). IUCN Red List of Threatened Species http://dx.doi.org/10.2305/IUCN... (2018).
  27. Cooke, J., Brownell Jr, R. L. & Shpak, O. Balaena mysticetus (Okhotsk Sea subpopulation). IUCN Red List of Threatened Species https://www.iucnredlist.org/sp... (2018).
  28.  

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